Fan wheel construction



Jan. 28, 1964 w. v. MILLMAN 3,119,553

' FAN WHEEL CONSTRUCTION Filed March 25, 1963 INVENTOR 3/6 7 8 WILLIAM v. MILLMAN BY 5% c. 4

ATTORNEY United States Patent Ofilice 3,119,553 Patented Jan. 28, 1954 3,119,553 FAN WEEEL CtrNdTRUCTEtT-N William V. Miiinian, Molina, ills, assignor to American Air Filter Company, inc, Louisville, Ky, a corporation of Delaware Filed tlar. 25, E63, Ser. No. 267,659 9 Claims. (6i. Blip-134) This invention relates to a fan wheel construction.

One object of the invention is the provision of a fan wheel construction of simple character and providing certain manufacturing economies while retaining adequate erformance characteristics. The simplicity of a construction according to the invention is exemplified in that the wheel may be formed solely of a hub and blades. The ri idity and stren th provided by the construction are sufficient that although the blades may be formed from light gauge material, they will adequately resist deformation and rupture at Wheel operating speeds well in excess of normal operating speeds for the service in which the wheel is intended.

The general configuration of a fan wheel according to the invention is essentially that of a straight-blade or paddle wheel fan in which the blades radiate from a central hub to which the root ends of the blades are secured. However, the wheel comprises a substantial departure from the conventional straight-blade wheel in that the width of the radially inner portion of each blade is divided into separate sections. Adjacent sections are bent or displaced away from each other so that the blade, in an end or edge View, has a forked inner portion. Thus, each blade as mounted on the hub has the root ends of its one or more alternate sections secured to the hub at one location, and the root ends of its one or more intermediate sections secured to the hub at another location spaced circumferentially around the hub from the first location. The radially outer portion of each blade is integral across the width of the blade.

In a presently preferred construction, the hub is provided with a series of circumferentially spaced, axially extending, slots. Each slot receives the root end of at least one alternate section of a blade, and the root end of at least one intermediate section of another blade.

The invention will be described in more detail in connection with the accompanying drawing wherein several embodiments are shown by way of example. In the drawing:

FTGURE l is an end view of a fan wheel according to the invention;

FIGURE 2 is an isometric view of one form of hub suited for use in the invention;

FIGURE 3 is an isometric view of a single blade before mounting on the FIG. 2 hub, and having an area outline suiting it for use in a single inlet, single width fan;

FIGURE 4 is a face view of the blade of FIGURE 3 as mounted on the hub of FIG. 2;

FIGURE 5 is an end view of FIGURE 4;

FIGURE 6 is an end view of a hub having a modified form of slot arrangement;

FIGURE 7 is a face view of a mounted blade having an area outline suitin it for use in a double inlet, single width fan; and

FIGURE 8 is a face view of a mounted blade having an area outline suiting it for use in a double inlet, double width fan.

Referring to the drawing, the fan wheel illustrated in FIGURE 1 is formed solely of a hub ll) and a series of blades 12 secured to the hub.

The hub (FIG. 2) is a cylindrical member including a central bore 14 for receiving the shaft which drives the fan wheel, and having a series of axially extending slots 16 equally spaced around the circumference of the hub. The cross-sectional shape of the slots 16 may be generally rectangular as illustrated in FIG. 2, or may have some other more complex shape in cross-section to afford greater resistance to loosening of the blades from the hub.

The blades 12 (FIG. 3) are each formed from a single sheet of material and comprise two main portions, a radially outer portion 18, and a radially inner portion 26. The outer portion is integral or unbroken across its width while the inner portion width is divided into sections by one or more generally radially extending cuts or slots. The single inlet, single width blade of the FIGS. 3-5 example has its inner portion divided into one section designated 22 and which will herein be called an alternate section, and an adjacent section designated 24 which will be called an intermediate section. In the example, alternate section 22 is displaced or bent one Way out of the plane in which the major part of the outer portion 18 lies, and the intermediate section 24 is displaced or bent in the opposite direction. Thus it may be said that the adjacent sections 22 and 24 lie in planes which are rotated away from each other along the line 25 dividing the inner and outer portion of each blade. The blade, as viewed from its edge, has a forked inner portion with the root ends 22a and 24a of the two sections parallel to each other but offset.

If a relatively light gauge material is used for the blades, stiffening ridges 26 following radiating lines outwardly from the hub may be provided as shown to stiffen the blades suificiently that they do not flex unduly during operation of the wheel.

The outer margin or tip portions 2% of the blades may be inclined one way or another out of the plane in which the major area of the outer portion lies to provide the performance characteristics desired of a particular fan wheel. All of the blades shown in the drawing having their tip portions inclined in the direction of rotation of the wheel so that in operation the performance characteristic obtained is essentially that of a forward-curved fan. However, it will be appreciated that the tip portions may be inclined backwardly so that the wheel will yield a performance characteristic of a backward-curved fan wheel, or the tip portions 28 may be left in the plane of the outer portion major area to obtain a performance characteristic of a straight-blade or radial-tip fan.

After all of the blades for a single wheel have been fabricated, they are mounted on the hub either singly or collectively in accordance with the character of the fastening arrangement used. Assuming first that simple rectangular slots as shown in FIG. 2 are provided, the blades may be moved radially, relative to the hub, into position. The root end 22a of alternate section 22 is re ceived by one of the slots, designated 16a, while the root end 24a of intermediate section 24 is received by another slot, designated Me, which is the second slot around the hub from slot 16a. As will be appreciated from FIG. 4, the root end 22a of alternate section 22 occupies only the left half of slot 16a, and the root end 24a of intermediate section 24 occupies only the right half of slot 16c. After the first blade is mounted, the next adjacent blade may be mounted by inserting the root end of its alternate section into the left half of slot 16b and the root end of its intermediate section into the right half of slot 16d. The third blade to be inserted will have the root end of its alternate section take up the remaining half (left) of slot with the root end of its intermediate section occupying the right half of slot 16s Successive blades are mounted around the hub until each slot has received two sections, one alternate from one blade and one intermediate from another blade.

Depending upon the blade and hub materials, the root ends of the sections may be secured to the hub in various ways in accordance with the strength required to resist the centrifugal forces generated in operation of the wheel. If the wheel is made of aluminum for example, with the attendant low centrifugal forces generated as compared to heavier materials, an industrial adhesive may be used to secure the root ends to the hub. With steel, a welded joint may be preferable. In other uses a friction fit may be adequate if the slots are undersized relative to blade material thickness, and the hub is heated to expand the slots during assembly.

In still other cases, a mechanical bond may be provided by forming the slots as illustrated in FIG. 6 with an enlarged inner portion 39, and a restricted neck portion 32 having a thickness corresponding generally to the thickness of the blade material. in such an arrangement the tips of the root ends of the inner portion sections are turned back upon themselves as indicated by the numeral 34 so that the root ends are locked within the slots with respect to movement in a radial outward direction. With the enlarged or retroverted root end arrangement, the blades must be moved into mounted relation to the hub by moving all of the blades, in their generally assembled relation, in an axial direction relative to the hub, and with each enlarged root end fed into its respective slot at the end of the hub.

The FIGS. 7 and 8 illustrations embody the same inventive principle as the blades heretofore described. However, here the radially inner portion is divided into three sections 36, 3d, and 4h respectively, and the intermediate section 38 is bent away from the plane in which the opposite alternate sections 36 and 4t) lie. Thus the root ends of the alternate sections 36 and 40 are finally secured in one axially extending slot 16, along with an intermediate section from another blade; and the intermediate section 38 of the illustrated blade will be secured in some other slot 16 along with opposite alternate sections of still another blade.

With a double-inlet, double-width blade as shown in FIGURE 8 it may be desirable because of its Width to break the diagonal edges 42 of the blade to some degree to increase the stiffness of the blade.

The construction according to the invention lends itself to fabricating fan wheels of very light weight for their size. For example, a wheel of about 15 inches in diameter made of 22 gauge aluminum blades and an aluminum hub weighs about as much as a cage type steel fan wheel of the same diameter. It will be appreciated that the light weight blades permit the fan to be operated at speeds considerably greater than is safe for the conventional cage type steel fan wheel.

As in the case of fan wheels generally, the performance characteristics and other qualities of the fan of this invention vary with the blade shape and surface configurations. In other words, with blade tip portion inclinations of one way or another, stiffener dispositions of one character or another, and one number or another of blades, the character of fan performance, noise and the like will vary. Thus, the specific design of the fan elements, within the scope of the invention, must for the most part be determined on a trial and error basis for the particular service in which the fan wheel will be employed.

It is noted that the specific structure illustrated and/ or described herein is for purpose of example only, and various departures in structural detail within the scope of the invention will occur to those skilled in the art. For example, the hub need not necessarily be slot-ted, but alternatively may be provided with independent means on its circumference to receive and secure the root ends of the blades. As another example, the blades may be stiffened by independent stiflener members secured to the blade surface instead of embossing the ridges 26 in the blades. Further, the circumferential space on the hub spanned by the alternate and intermediate sections of a single blade may in some cases be the space between adjacent slots, and in other cases be the space between every third or fourth slot, for example, each case being determined in accordance with the desired end result.

The invention claimed is:

1. A fan wheel of paddle wheel character, comprising:

(a) a hub with a series of generally radiating blades secured thereto;

(b) each blade having the width of its radially inner portion divided into separate sections alternately displaced one way and another way with the root end of each section being generally parallel to the axis of said hub, and with the root end of each section of a blade as mounted offset circumferentially around said hub from the root end of the adjacent section of the same blade.

2. A fan wheel as specified in claim 1 wherein:

(a) said hub includes a number of axially extending slots corresponding to the number of said blades; and

(b) each slot receives a section from at least two different blades.

3. A fan wheel of paddle wheel character, comprising:

(a) a hub with a series of generally radiating blades secured thereto;

(b) each blade having the width of its radially inner portion divided into separate sections bent away from each other to define an acute angle therebetween as viewed from the edge of said blade, the root ends of said section adapted to be secured to said hub being generally parallel to the axis of said hub, with the root end of one section of a blade secured to said hub along an axially extending line offset circumferentially around said hub from the root end of each adjacent section of the same blade.

4. A fan wheel as specified in claim 3 wherein:

(a) the root ends from sections of two different blades are secured in aligned relation along each of the axially extending lines on the hub.

5. A fan wheel comprising:

(a) a hub;

(12) a series of blades secured to and radiating from said hub, each blade being formed from a single sheet;

(0) the radially inner portion of each blade including slot means dividing the width of said inner portion into at least one alternate section and one intermediate section lying in diiferent, rotated planes; and

(d) means for securing the root end of said alternate section along one axially extending line on said hub, and the root end of said intermediate section along another axially extending line spaced around said hub from said one line.

6. A fan wheel comprising:

(a) a hub having a series of generally radiating blades secured thereto;

(b) each blade having the width of its radially inner portion separated into alternate and intermediate sections, at least one of said sections being displaced out of the initial plane of said sections, but with the axes of said root ends being generally parallel;

(0) each blade being mounted on said hub with the root end of each alternate section being secured to said hub along one axially extending line on said hub, and the root end of each intermediate section being secured to said hub along another axially extending line spaced around said hub from said one axially extending line.

7. A fan wheel comprising:

(a) a hub having a series of generally radiating blades secured thereto;

(b) each blade having a radially inner and a radially outer portion;

(c) said radially outer portion being unbroken across its width;

(d) said radially inner portion including alternate and intermediate sections across its width displaced from each other to form, as viewed from the edge of said 5 6 blade, an acute angle which opens toward said hub; each blade being secured to said hub with the root (e) each blade being mounted on said hub with the ends of adjacent ones of its sections spaced around root end of each said alternate section being secured the hub from each other, but parallel to each other to the hub at a location circumferentially spaced and to the axis of said hub. around the hub from the location at which the root 9. A fan Wheel as specified in claim 8 wherein: end of each said intermediate section of the same (a) said means to receive said root ends includes axialblade is secured to the hub. ly extending slots; and 8. A fan wheel comprising a hub and blades secured (b) each of said slots receives the root ends of sections thereto: of at least two separate blades.

(a) said hub being of generally cylindrical shape and 10 including means at its circumference to receive the References Cited in file Of this Patent root ends of said blades; UNITED STATES PATENTS (b) each of said blades being formed from a single sheet including a radially outer portion unbroken 9 .7 8 across its width, and a radially inner portion divided 15 3045986 g J 1962 across its width into separate sections lying in planes rauen erger u y rotated from each other so that each blade, as viewed FOREIGN PATENTS from its edge, has a forked inner portion; and 332 859 Great Britain July 31, 1930 

1. A FAN WHEEL OF PADDLE WHEEL CHARACTER, COMPRISING: (A) A HUB WITH A SERIES OF GENERALLY RADIATING BLADES SECURED THERETO; (B) EACH BLADE HAVING THE WIDTH OF ITS RADIALLY INNER PORTION DIVIDED INTO SEPARATE SECTIONS ALTERNATELY DISPLACED ONE WAY AND ANOTHER WAY WITH THE ROOT END OF EACH SECTION BEING GENERALLY PARALLEL TO THE AXIS OF SAID HUB, AND WITH THE ROOT END OF EACH SECTION OF A BLADE AS MOUNTED OFFSET CIRCUMFERENTIALLY AROUND SAID HUB FROM THE ROOT END OF THE ADJACENT SECTION OF THE SAME BLADE. 